Terminal bushing for power cables



Dec. 28, 1948; c. E. BENNETT ETAL TERMINAL BUSHING FOR POWER CABLES Filed Aug. 9, 1944 mi l/ll hm ATTORNEY m mm a m Patented Dec. 28, 1948 UNITED STATES PATENT OFFICE TERMINAL BUSHING FOR POWER, CABLES Charles E. Bennett, Ridgewood, and Paul V. White, Rochelle Park, N. 3., assignors to The Gkonite-Cailender Cable Company, Incorporated, Paterson, N. 3., a corporation of New Jersey Application August 9, 1944, Serial No. 548,688

under superatmospheric pressure of the order of two hundred pounds per square inch.

With terminal bushings for this type of cable system, it has been difficult to obtain a satisfactory seal at the terminal end of the bushing which will hold and yet not crack the cement seal between the insulating casing of the bushing and the bronze flange as presently used owing to the pressure necessarily exerted to effect a seal which will hold the superatmospheric pressures above referred to.

The present invention provides a construction wherein the necessity of metal to procelain contact is entirely avoided.

The accompanying drawing shows an embodiment of our invention in part sectional elevation.

Referring to the drawing in detail: 2 designates a pair of insulated cable conductors which are to be terminated. l designates a riser through which the conductors extend, and which carries the insulating casing 6 of the bushing.

The method of mounting the porcelain insulating casing on the riser pipe 4 forms no part of our invention and hence will not be described in detail. It is to be understood, however, that the lower end of the casing is sealed in place.

The inner ends of the conductors 2 which extend into the insulating casing, and are to be terminated, are stripped of insulation and their bared ends 8 are mechanically connected by the use of a velocity bonding press and velocity driver into copper lugs I0. A copper connector [2 projects from the upper end of the insulating casing 6, the inner end of this connector being clamped by bolts 14 between the copper lugs III. The connector II, it will be appreciated, is to be connected to a bus bar or other current conducting or distributing member.

In order that a seal may be provided about the connector l2 where the same projects through the top of the insulating casing 6, and at the same time avoid a metal to insulator contact, theconnector 12 adjacent its lower or inner end is provided with a metal ring I6 which is welded or otherwise rigidly secured to theconnector.

The bore l8 in the upper end of the insulating casing 6 is appreciably larger in diameter than the connector, and is countersunk at each end, as shown at 20 and 22, respectively, to receive tapered non-metallic sealing gaskets 24 and 26.

Just below the gasket 24 the connector I! car- 2 ries a loose metal compression ring 28 which bears against the inner face of the gasket. Surrounding the connector 42 and lying between the loose compression ring 28 and the fixed connector ring !6 previously referred to is compression spring 30.

It is to be noted that the outside diameter of the compression ring 28 is slightly less than the inside diameter of the outer end of counter-bore 20, so that the ring is always out of contact with the insulator.

The connector [2 also carries loose compression ring 32 which rests upon the sealing gasket 26. The outside diameter of this ring is smaller than the diameter of the large end of counterbore 22 so that this ring is kept out of contact with the insulator.

The outer end of the connector which is threaded carries a nut 34.

It will be apparent that when the nut 34 is turned down the non-metallic sealing gaskets 24 and 26 will be compressed about the connector, hermetically to seal the'same at the insulating casing, the extent of compression being controlled by the travel of the nut 34 and compression of the spring 30.

As explained at the outset of this description, this terminal bushing is particularly well adapted for use in connection with terminating cable systems of the type wherein the insulated conductors are loosely enclosedin a pipe line filled with insulating fluid which is maintained at a. high superatmospheric pressure, it being appreciated that this fluid also fills the insulating casing B. The construction provided by our invention efiectively seals the upper end of the insulating casing against escape of this fluid, this sealing, it will be apparent, being obtained without contact of the terminal end of the insulating casing 6, with metal at any place throughout its whole extent. As a consequence of this construction, we not only obtain the desired seal, but we eliminate at the same time all danger of damage to the insulating casing due to the diiierence in the coefllcient of expansion and contraction of the casing and the metal members at the terminal end of the bushing.

It will be appreciated also that by employing the compression spring 30 between a rigid part of the connector, in this case rigid ring l6, and the gasket 24 we are assured of maintenance of a tight seal between the connector l2 and the in sulating casing 6 even though there may be some slight elongation of the cable conductors 2, the lugs l0 and the connector itself, due to heating under load.

It is to be understood that changes mat be made in the details oi construction and arrangement of parts hereinabove described without departing the spirit and scope of our invention.

What oir is:

l. A terminal for electric cables comprising in combination an insulating casing under internal superatmospheric pressure or receiving a cable conductor which is to be terminated, a connector for attachment to the terminal end of the cable conductor, said connector pro ecting through the terminal end of the insulating casing, an abut men; on said connector within the insulating casing and rigid with the connector, a non-metallic gasket surrounding the connector and interposed between it and the inner face of the insulating casing, a compression ring for said gasket loose upon the connector, a spring under compression carried by the connector between said connector abutment and said compression ring, a non-metallic gasket at the outer face of the terminal end of the insulating casing between the insulating casing and the connector, a compression ring therefor, and a nut threaded upon the connector and bearing against said last mentioned compression ring and maintained thereby out of contact with said insulating casing, said compression rings, nut and connector being out of contact with the insulating casing, tightening of said nut compressing said gaskets between their respective compression rings and the insulating casing.

2. A terminal for electric cables comprising in combination an insulating casing under internal superatmospheric pressure for receiving a cable conductor which is to we terminated, a connector rigidly secured to the terminal end of the cable conductor within the insulating casing, said con nector projecting through the outer end of said casing, a shoulder on said connector within said casing, said shoulder being rigid with the con" hector, a bore in the outer end of said casing through which said connector extends and projects from the casing, said bore being slightly larger in diameter than the connector, the entry and exit ends of said bore being countersunk, gaskets in said countersinks surrounding said connector, a compression ring for each gasket loosely surrounding said connector, a compression spring on the connector between said connector shoulder and the adjacent compression ring, and a out on the connector for egagement with the other of said compression rings to efl'ect com pression 01 said gaskets between the compression rings and the insulating casing.

3. A terminal for electric cables comprising in combination an insulating casing under internal superatmospheric pressure for receiving a cable conductor which is to be terminated, a connector rigidly secured to the terminal end of the cable conductor within the insulating casing, said connector projecting through the outer end of said casing, a shoulder on said connector within said casing, said shoulder being rigid with the conhector, a bore in the outer end of said casing through which said connector extends and projects from the casing, said bore being slightly larger in diameter than the connector, the entry and exit ends of said bore being countersunk, nonmetallic gaskets in said countersinks surrounding said connector, a metal compression ring for each gasket loose upon said connector, each ring being smaller in diameter than the bore in the insulating casing, a compression spring on the connector between said connector shoulder and the adjacent compression ring, and a nut threaded upon the connector for engagement with the outer face of the other of said compression rings, whereby a non-metallic seal is provided between the connector and said insulating casing upon tightening of said nut to efiect compression of the said gaskets between their respective compression rings and the insulating casing.

CHARLES E. BENNETT. PAUL V. WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PAIENTS Number Name Date ,211,061 Bock Jan. 2, 1917 1,891,213 Edmonds Dec. 13, 1932 2,000,653 Wilkinson May 7, 1935 2,315,623 Jacobi s. Apr. 6, 1943 2,354,191 Bennett July 25, 1944 FOREIGN PATENTS Number Country Date 1 7,478 Great Britain 1918 638,717 Germany Nov. 21, 1936 202,926 France Oct. 5, 1937 

